U.S. patent application number 17/092503 was filed with the patent office on 2022-05-12 for system and method for continuous fabrication of graded structured units using additive manufacturing.
This patent application is currently assigned to Advanced Manufacturing LLC. The applicant listed for this patent is Advanced Manufacturing LLC. Invention is credited to Dongsheng Li, Thomas Maloney.
Application Number | 20220149411 17/092503 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-12 |
United States Patent
Application |
20220149411 |
Kind Code |
A1 |
Li; Dongsheng ; et
al. |
May 12, 2022 |
System and Method for Continuous Fabrication of Graded Structured
Units Using Additive Manufacturing
Abstract
A system and method of continuous fabrication of multi-material
graded structures using additive manufacturing is disclosed. Using
multi-material feedstocks and optimized processing parameters, the
gradient on composition and structure are controlled to achieve
smooth transition from one functional component to another
functional component. A multi-material graded structure is produced
as the feedstocks are transported from the feedstock reservoir
system comprised of many different materials. Interface transition
from one functional layer to the next is gradient, controlled by
feedstock mixture ratios based on the flow rate control for the
feedstock system. Composition includes chemical composition,
physical composition, and porosity. Continuous automatic additive
manufacturing method makes the fabrication more efficient and
avoids joining problems. This method finds application in
fabrication of a fuel cell, battery, reformer and other chemical
reaction and process units, including structures made of multiple
units, such as stacks, that incorporate multiple functional
components.
Inventors: |
Li; Dongsheng; (Farmington,
CT) ; Maloney; Thomas; (Hebron, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Advanced Manufacturing LLC |
East Hartford |
CT |
US |
|
|
Assignee: |
Advanced Manufacturing LLC
East Hartford
CT
|
Appl. No.: |
17/092503 |
Filed: |
November 9, 2020 |
International
Class: |
H01M 8/1253 20060101
H01M008/1253; B29C 64/268 20060101 B29C064/268; B29C 64/118
20060101 B29C064/118; B29C 64/393 20060101 B29C064/393; B33Y 80/00
20060101 B33Y080/00 |
Claims
1. An apparatus comprising a multi-material graded structure formed
from materials that are mixed and melted into a melt pool utilizing
a high energy source.
2. The apparatus of claim 1 wherein the multi-material graded
structure comprises a solid cathode, a solid anode, and a solid
electrolyte.
3. The apparatus of claim 2 wherein the electrolyte comprises
yttria-stabilized zirconia (YSZ).
4. The apparatus of claim 1 where the multi-material graded
structure is a solid oxide fuel cell.
5. The apparatus of claim 2 wherein the cathode comprises lanthanum
strontium manganite (LSM).
6. The apparatus of claim 2 wherein the electrolyte comprises
yttria-stabilized zirconia (YSZ), the anode comprises NiO, and the
cathode comprises lanthanum strontium manganite (LSM).
7. The apparatus of claim 1 wherein the multi-material graded
structure comprises a battery that includes a positive grid, a
positive plate, a separator, a negative grid and a negative
plate.
8. The apparatus of claim 1 wherein the multi-material graded
structure comprises at least one of an energy storage unit, an
energy conversion unit, and a chemical reformer.
9. The apparatus of claim 1, wherein the structure is graded in at
least one of porosity, chemical composition, architecture, and/or
morphology.
10. A method for producing a multi-material graded structure where
an additive manufacturing process utilizing a high energy source
and multiple material storage is used to produce a melt pool of
multi-materials that is formed from materials fed into the melt
pool at a precise and predetermined rate and mixture and where the
multi-material from the melt pool is deposited upon a substrate to
form a solid graded multi-material.
11. The method of claim 10 wherein the solid graded multi-material
comprises a solid cathode, a solid anode, and a solid
electrolyte.
12. The method of claim 10 wherein the solid multi-material formed
from the melt pool comprises at least one of an energy storage
unit, an energy conversion unit, and a chemical reformer.
13. The method of claim 10 wherein the continuous fabrication of
the graded structured units is accomplished using additive
manufacturing.
14. The method of claim 13 wherein the additive manufacturing
method includes at least one of powder additive manufacturing and
wire feed additive manufacturing.
15. The method of claim 13 wherein the additive manufacturing
method includes at least one of powder feed additive manufacturing
and powder bed additive manufacturing.
16. The method of claim 13 wherein the high energy source comprises
at least one of a laser source, electron beam source, and kinetic
energy source.
17. The method of claim 10 wherein the multi-material graded
structure is configured to be included in a solid oxide fuel
cell.
18. A method of utilizing a modified job code computer file for
Computational Aided Machining in an additive manufacturing machine
configured to form a multi-material graded structure, the computer
file comprises code to regulate material mix ratios and flow
rates.
19. The method of claim 18, wherein the modified job code computer
file comprises code to regulate the flow rate of one or more powder
reservoirs to form one or more layers of the multi-material graded
structure.
20. The method of claim 18, wherein the modified job code computer
file comprises code to regulate the flow rate of each powder
reservoir to form layers in the multi-material graded structure.
Description
BACKGROUND
[0001] There are many different methods to fabricate graded
components that have been proposed and developed. Chemical vapor
deposition, tape casting, screen printing, slurry-spraying,
spray-painting, and slurry coating all have been reported in the
literature. Due to the limitations of processing methods, most of
these methods are not continuous. Production disruption that occurs
when changing the raw material decreases the efficiency of the
process, making large production infeasible. Furthermore, most of
the composition gradients are reached by two or three layers with
different compositions, which makes the gradient still large and
discontinuous. There is a lack of a continuous processing method to
reach smooth composition graded structure with high production
efficiency. It would be useful to overcome these limitations.
SUMMARY
[0002] One embodiment disclosed herein is apparatus comprising a
multi-material graded structure formed from materials that are
mixed and melted into a melt pool utilizing a high energy
source.
[0003] Another embodiment disclosed herein is method for producing
a multi-material graded structure where an additive manufacturing
process utilizing a high energy source and multiple material
storage is used to produce a melt pool of multi-materials that is
formed from materials fed into the melt pool at a precise and
predetermined rate and mixture and where the multi-material from
the melt pool is deposited upon a substrate to form a solid graded
multi-material.
[0004] A further embodiment described herein is a method of
utilizing a modified job code computer file for Computational Aided
Machining in additive manufacturing machines with materials mix
ratio description and implementation.
[0005] Other embodiments described herein include a system and
method for continuous fabrication of graded structured units using
additive manufacturing. Multi-material graded structure includes
composition gradient, porosity gradient, morphology gradient, grain
size gradient, and structural gradient.
[0006] According to yet another embodiment, a method is provided
for fabrication of a composition gradient fuel cell unit with three
components: anode, electrolyte and cathode. Gradient structure is
applied at the interface of components. The unit can be fabricated
with a laser beam powder feed additive manufacturing machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 illustrates graded structure of units in general
composed by functional components with graded interface.
[0008] FIG. 2A compares conventional and graded solid oxide fuel
cell configuration.
[0009] FIG. 2B shows the size of the various graded components for
one embodiment of the solid oxide fuel cell configuration.
[0010] FIG. 3 illustrates graded structure of battery composed by
functional components with graded interface.
[0011] FIG. 4 shows a process flow of manufacturing of graded
structured unit and components using additive manufacturing.
[0012] FIG. 5 shows implantation of one stage of the process
illustrating material flow to reach graded structured unit from
powder reservoirs to additive manufactured components and
units.
[0013] FIG. 6 shows traditional information flow in another stage
of the process, processing optimization identified in FIG. 4.
[0014] FIG. 7 shows graded structure manufacturing multi-material
information flow in stage 300, processing optimization identified
in FIG. 1.
[0015] FIG. 8 shows the setup of the laser and powdered material
feed used in directed energy deposition (DED) for forming the melt
pool on the substrate.
[0016] FIG. 9 shows setup of multiple material feed with control to
reach multi-material graded structure in solid oxide fuel cell.
[0017] FIG. 10A shows a micrograph of a LSM cathode fabricated by
additive manufacturing.
[0018] FIG. 10B shows a micrograph of a YSZ electrolyte fabricated
by additive manufacturing.
[0019] FIG. 10C shows a micrograph of a NiO anode fabricated by
additive manufacturing.
[0020] FIG. 11A shows a bird's eye view and micrographs of YSZ
deposited on NiO layers with size of 2.5 cm*2.5 cm.
[0021] FIG. 11B shows a portion of the multi-material graded
structure in 11A that has been enhanced for viewing of the
microstructure.
[0022] FIG. 12 is a depiction of the components of a fuel cell and
the electrochemical process that produces electricity from a fuel
source.
[0023] FIG. 13 is a depiction of the multi-material gradient
structure showing the gradients between the electrolyte and the
anode layer in a fuel cell.
[0024] FIG. 14A is a depiction of a fuel cell made with additive
manufacturing.
[0025] FIG. 14B is a cut away of FIG. 14A showing the internal
structure.
DETAILED DESCRIPTION
[0026] This disclosure relates to continuous fabrication of graded
structure units using additive manufacturing. Using multi-material
feeds and optimizing the fabrication processing parameters, the
gradient material composition is controlled precisely to produce a
smooth transition from one functional material component to another
functional material component.
[0027] Continuous fabrication of graded structure units using
additive manufacturing can be utilized to produce systems and
components having tailored properties and structural designs that
deliver low cost, high performing products. Energy conversion
devices, such as fuel cells and batteries, can be fabricated with
graded interfacial structures and in any geometry. This obviates
the performance penalties and traditional design constraints that
currently exist for electrochemical systems that are fabricated
with stacks of flat plates of different materials stacked upon one
another with non-graded interfaces. Furthermore, the methods
proposed before could not produce free form structure
[0028] A compositional and/or morphological and/or structural
gradient in component material is preferred in many engineering
applications. For example, components with gradient porosity have
been applied in medical implants, heat insulation, and thermal
shock resistant structures. To join dissimilar materials and
decrease the mismatch in properties at interface, functionally
graded materials have been developed to achieve unique properties
and reach high performance. In fuel cell components, graded
materials with porous gradient or chemical composition gradient
have been developed and utilized. It was reported that graded
structure components in fuel cells reduced interfacial polarization
resistances and improved electrochemical performances. Graded
structure in anodes, electrolytes and cathodes have all been
reported. Another importance of graded structure in fuel cell lies
on the requirement of oxygen reduction reaction, which happens at
the triple phase boundary, co-incidence of oxygen gas, electronic
conductor electrode and ionic conductor electrolyte. Graded
structure increases the effective length of the triple phase
boundary, improving the overall electrochemical performance.
[0029] This described embodiments can replace the conventional
methods for fabricating components and systems, such as solid oxide
fuel cells (SOFC) and other chemical reactor systems. For more than
four decades, SOFCs have been made using conventional methods such
as tape casting, calendar rolling, chemical/electrochemical vapor
deposition, among others. These methods are costly, time-consuming,
require processing in high temperature furnaces, and are
constrained to planar or tubular design configurations. And
significantly, these conventional methods are not continuous and
they do not allow for materially-graded structures. Hence, the
interfaces where differing materials meet are the source of
performance degradation and subsequent failure. Attempts to
overcome these deficiencies have led to lower temperature tolerant
materials (600.degree. C.-800.degree. C.) which result in lower
overall efficiency. This described embodiments enable fabrication
of systems such as SOFCs such that the interfacial properties are
satisfactory and sustained high temperature (1,000.degree. C.),
high efficiency operation is enabled. The components and parts can
be made via a continuous manufacturing process, and geometries for
builds are not limited to planes and tubes. The disclosed
embodiment find application in, but not limited to, fuel cells,
energy storage units, energy conversion units, chemical reformers,
and so on.
[0030] The embodiments described herein utilize additive
manufacturing methods in fabrication. The manufacturing methods
include but are not limited to powder additive manufacturing and
wire feed additive manufacturing. The methods include but are not
limited to powder feed additive manufacturing and powder bed
additive manufacturing. The methods include but are not limited to
those that employ laser source, electron beam source, and/or
kinetic energy source additive manufacturing methods.
[0031] One embodiment focuses on fabrication of graded structure.
Graded structure includes but not limited to gradients in porosity,
chemical composition, architecture, and/or morphology. The general
purpose of graded structure is to reach the gradient of properties,
including but limited to mechanical, electrical, chemical and
magnetic properties.
[0032] A graded structure with multiple function layers is
illustrated in FIG. 1. Most units are composed by multiple layers
or components. Each layer or component comprises different
materials. The interface of layers usually has sharp contrast of
property. For example, thermal shock may be introduced due to
difference in thermal expansion coefficients. A graded structure is
introduced at the interface to reduce the sharp contrast. As shown
in FIG. 1, the interfaces or boundaries are blurry. By introducing
the gradient structure at the interface transition in fuel cells,
the change in thermal expansion coefficient and mechanical
properties are gradient. The life of the SOFC will be extended due
to the reduced thermal induced stress during operation cycles.
Furthermore, the efficiency of the fuel cell unit will be increased
by increasing the interface area between the electrode and
electrolyte. The interfaces of layers in FIG. 1 is linear or
planar. The present embodiments are not limited to planar or tube
shaped interface. Due to the flexibility of additive manufacturing
method, there is no limitation to the shape of interface.
[0033] The capability to customize electrode, electrolyte, and
interconnecting functional elements can lead to increased operating
efficiency, decreased performance degradation rates, and increased
number of on/off cycles. Overall system efficiency can be defined
as the electrical power delivered divided by the lower heating
value of fuel consumed. Additional efficiency gains can be accrued
if waste heat is productively utilized. On/off cycles induce
thermal stresses due to thermal expansion rate differences between
the electrodes, electrolytes, and interconnect. Graded interfaces
are expected to lessen the thermal stresses during on/off
cycles.
[0034] One example of the graded structure is applied in a solid
oxide fuel cell, as illustrated in FIG. 2A. The left figure shows a
conventional configuration of a solid oxide fuel cell. Components
of different functional layers are stacked together. The layers
include but not limited to interconnect, cathode, electrolyte, and
anode. The layers are not limited to planar or tube configuration.
The stacks are connected by, but not limited, physical contact,
deposition, diffusion, joining, etc. In a conventional
configuration, the boundaries between the functional layers are
clear. The right figure shows a graded configuration of solid oxide
fuel cell in accordance with embodiments described herein.
Interfaces of the functional layers are blurry. One non-limiting
example is a structure in which the electrolyte comprises yttria
stabilized zirconia (YSZ), and the anode comprises nickel reduced
from nickel oxide. The interface between the YSZ and nickel oxide
comprises multiple very thin layers smoothly changing the chemical
composition with a small gradient.
[0035] A solid oxide fuel cell has two categories: anode support or
cathode support. The size of the unit cell is in the range of
4-2500 cm.sup.2 with side 5-50 cm. The thickness of the electrolyte
is between 3-300 .mu.m. The gradient change from electrode to
electrolyte is between 10 .mu.m.sup.-1-10 mm.sup.-1. In other
words, 20% composition change within 4-80 .mu.m. Several different
embodiments for SOFC structures can be considered, depending upon
desired geometry (planar, tubular, monolithic, unique geometry) of
final product. In one tubular embodiment, the cathode is relatively
thick compared to the electrolyte, anode, and interconnect. For
this case, a graded structure may be envisioned as shown in FIG.
2B. The grading between cathode and electrolyte may be uniform at
10% grading per 200 .mu.m thickness. Similarly, the anode in such
embodiment may be graded at a higher level, at 10% grading per 15
.mu.m thickness. This is shown in FIG. 2B where a graded SOFC
configuration made by directed energy deposition (DED) (10% grading
per 200 .mu.m) is shown.
[0036] Alternative grading scales may also be implemented. For
example, the cathode in FIG. 2B may be comprised of pure, bulk
cathode material at its interior, and the grading may occur only
near the interfaces. In this case, the cathode-electrolyte
structure may be graded at 10% per 10 .mu.m thickness, assuming
only the 100 .mu.m portion of the cathode, closest to the
electrolyte, is graded. Other embodiments may be fabricated with
electrolyte, anode, or interconnect comprising the thickest
component.
[0037] A similar approach is applied to other devices, such as
battery, as illustrated in FIG. 3. Functional layers in a battery
include, but are not limited to, positive grid, positive plate,
separator, negative grid and plate. The interfaces between the
functional layers are designed to be transient with graded
structure. The present embodiment is not limited to fuel cells,
battery, chemical transformer.
[0038] FIG. 4 shows the process flow of system in present
embodiment. It includes but not limited to three steps: product
design, materials design and process optimization. The overall
process is designated as 96. In stage 100, product design, the CAD
file with geometry information will be created to satisfy the
function of parts. In stage 200, materials design, the material
composition will be decided to reach the mechanical, electrical,
and chemical requirement for parts. Gradient of chemical
composition is also decided in this stage. In stage 300, additive
manufacturing, the processing parameters and procedures will be
optimized to achieve desired microstructure and superior
properties.
[0039] The detailed description of implantation of materials
design, including material flow in stage 200 is illustrated in FIG.
5. The powders are stored in a series of reservoirs, 201, 202, . .
. . Composition is controlled by the ratio of powder mixed from the
reservoirs. Smooth transition between the functional layers is
reached by controlling the flow rate of the multiple material pool.
Flow of each material pool is controlled by its own flow rate
control 211, 212, . . . . The mixed powder is mixed and carried to
powder tube 221. Then feed to additive manufacturing machine 300.
The mixed powder from multi-material powder reservoirs are fed to
nozzle in powder feed additive manufacturing machine or powder
delivery system in powder bed additive manufacturing machine.
[0040] Traditional data flow in additive manufacturing is
illustrated in FIG. 6. CAD file 160 obtained from stage 100,
product design, are converted to slice files 162. Then the slice
files are transferred to machine CAM file in Job code 164. These
file can be, for example, in the format of G-code or M-code,
depending on the machine and terminology. The job code is uploaded
or transferred to an additive manufacturing machine control panel
166 to initiate the building processing.
[0041] In contrast, the data flow in present embodiments disclosed
herein has more controls and selections, as shown in FIG. 7. CAD
files 101 from stage 100 are fed into slicing tools to generate
slice files 302. With powder composition input files 303, generated
from stage 200 in material design, the slice files are transferred
to G-code or Job code 304. The G-code in the present embodiment has
more information in the material selection and powder feed rate
ratio for multiple powder reservoirs. Guided by optimized
processing parameters 306, the part with transient interface are
produced by additive manufacturing processing 305 based on the
G-code 304. The slicers or slicing tools may also be coupled with a
machine learning algorithm to optimize gradient generation and
produce a generative design.
[0042] The embodiments described herein may utilize a laser-based
(DED) additive manufacturing process to continuously fabricate
multi-material graded structures in conventional and novel
geometries. FIG. 8 illustrates the implementation of present
embodiment in fabrication of graded structured solid oxide fuel
cell unit using DED with multi material reservoirs. The DED process
is initiated when a laser beam is directed onto a starting
substrate material. Laser beam characteristics, such as power, beam
size, and distance from the substrate are controlled in a manner
that optimizes the desired build. The laser energy imparted to the
substrate creates a liquid melt pool into which new materials are
added. Materials are added by inducing flow of such materials from
storage hoppers, through a connecting feed tube, into the melt
pool. The laser beam position and corresponding feed tube position
are continuously moved in a controlled manner to form the desired
geometry. New material that that flows through the feed tube
originates from storage hoppers. Multiple storage hoppers, each of
which can be filled with different materials, allow for parts to be
built with different materials and gradations of materials. As
shown in FIG. 9, three powder hoppers are utilized: one for YSZ
electrolyte, one for NiO anode, and one for lanthanum strontium
manganite (LSM) cathode. Flow rate of powder material from each
hopper to the fed tube is controlled in this process. Precisely
controlled powder mix with desired ratio is fed into tube and
further to powder spray nozzle. In FIG. 8, the depiction of the
laser forming the melt pool on a substrate while powdered material
is impinged upon the melt pool shows the process of DED in action
as a multi-material graded structure is deposited on a
substrate.
[0043] The fabricated components that are fabricated based on the
present embodiment are characterized. Micrographs of three major
components in solid oxide fuel cells are illustrated in FIG. 9. The
cathode fabricated from LSM powder, electrolyte from YSZ powder and
anode from NiO powder shows continuous and solid microstructure as
shown in FIG. 9. No pores or voids are observed in the
micrographs.
[0044] FIGS. 10A, 10B, and 10C show pictures of 2.5 cm*2.5 cm unit
with 100 .mu.m thick YSZ on 200 .mu.m thick NiO. The interface
between YSZ and NiO are graded structure with gradient transition
on chemical composition. Pictures show the continuous and solid
surface of electrolyte YSZ. Micrographs also show continuous
microstructure in micrometer scale. The graded structure at
interface for solid oxide fuel cell components has been reached
successfully by DED.
[0045] The depiction in FIG. 10A shows micrographs of the cathode
of the fuel cell, FIG. 10B shows a micrograph of the electrolyte of
the fuel cell, and FIG. 10C shows a micrograph of the anode of the
fuel cell. The cathode, electrolyte, and the anode have all been
produced using a multi-material graded structure. The material has
been deposited using a DED process where powdered material is
formed into a melt pool by a high energy source such as a laser and
deposited on a substrate.
[0046] The depiction in FIG. 11A shows a fuel cell portion
manufactured with additive manufacturing while FIG. 11B depicts a
magnified portion of the multi-material graded structure in FIG.
11A for more detail of the deposition of the powdered material that
has been subsequently melted in the melt pool and applied to the
substrate.
[0047] The depiction of the fuel cell in FIG. 12 shows the
separation of the cathode, the electrolyte, and the anode. It also
shows the electrochemical cycle where fuel is put into the
fuel-cell and heat, electricity, and water are products of the
reaction. This depiction shows distinct layers of the anode
electrolyte cathode, unlike the multi-material graded structure
that is formed by the additive manufacturing process utilizing the
DED process and powdered materials the form a melt pool which is
subsequently deposited on a substrate.
[0048] The multi-material graded structure that is shown in FIG. 13
depicts the interface between the electrolyte anode layers of the
fuel-cell. It may be seen that the interface is made up of a
multi-material graded structure that changes gradually from one
layer to the next.
[0049] FIG. 14A shows a reactor 700 with complex channeled
structure, which is not manufacturable by traditional manufacturing
method. FIG. 14B is a cut away of the additive manufactured
structure in FIG. 14A showing the interior channels. The only
feasible method to fabricate it is through additive manufacturing.
Using additive manufacturing methods with multi-material
capability, it is possible to fabricate the complex structure with
both a composition gradient and a structure gradient. The internal
structure 702 may be curvilinear or other complex shapes while the
exterior 701 may be a plain in shape three dimensional polygon such
as a cylinder or cube.
[0050] A solid oxide fuel cell has two categories: anode support or
cathode support. The size of the unit cell is in the range of
4-2500 cm.sup.2 with side 5-50 cm. The thickness of the electrolyte
is between 3-300 .mu.m. The gradient change from electrode to
electrolyte is between 10 .mu.m.sup.-1-10 mm.sup.-1. In other
words, 20% composition change within 4-80 .mu.m. Several different
embodiments for SOFC structures can be considered, depending upon
desired geometry (planar, tubular, monolithic, unique geometry) of
final product. In one tubular embodiment, the cathode is relatively
thick compared to the electrolyte, anode, and interconnect. For
this case, a graded structure may be envisioned as shown in FIG. 1.
The grading between cathode and electrolyte may be uniform at 10%
grading per 200 .mu.m thickness. Similarly, the anode in such
embodiment may be graded at a higher level, at 10% grading per 15
.mu.m thickness.
[0051] The defined range of controlled additive manufacturing
method process parameters that result in quality builds of graded
of graded structures of any geometric shape. Control and definition
of the additive manufacturing process parameters dictates the
quality of the continuously built parts. The defined and/or
controlled parameters during continuous build include: type of
laser, laser power, laser wavelength, laser spot size, laser focal
point, laser beam profile, melt pool size, total material flow rate
through feed tube, flow rate of each material from each powder
hopper, write speed, individual layer dimensions, distance from
laser head to part, and distance from powder feed tube to part.
[0052] In some cases, the defined and/or controlled parameters
during continuous build include:
[0053] The type of laser technologies including gas laser (such as
CO.sub.2 laser), chemical laser (such as hydrogen fluoride laser),
solid state laser (such as ytterbium doped glass fiber laser), dye
laser (such as coumarin 102 laser), metal-vapor laser (such as
helium cadmium laser). In some cases, laser power for additive
manufacturing spans the range from less than 20 watts up to 20,000
watts in constant power or pulsed modes. Laser wavelengths
typically ranging from 0.193 .mu.m to 10.6 .mu.m, depending on type
of laser. Laser spot size depends on laser system and can be less
than 28 .mu.m and up to and exceeding 500 .mu.m. Laser focal point
can be positioned at converging or diverging sections of the laser
beam. The laser beam profile can be "top hat" or Gaussian, or
another suitable profile. The laser beam quality factor is
typically between 0.3-20 mm*mrad, although other quality factors
may be used.
[0054] In embodiments, the melt pool size is controlled by a
combination of laser type, wavelength, power, beam size, write
speed, material flow (in the case for directed energy deposition).
Total material flow rate through the feed tube typically has a
typical range of about 0.5-5 grams/minute depending upon powder
density. The flow rate of each material from each powder hopper is
proportional to the number of hoppers scaled to the total material
flow rate through the feed tube. In some cases, the write speed of
the DED process is between 0.5-3.0 cm/sec.
[0055] The individual layer dimensions range from less than 20
.mu.m to more than 150 .mu.m, or about 20 .mu.m to about 150 .mu.m,
or about 30 .mu.m to about 100 .mu.m depending upon powder particle
size, laser power size and laser spot size.
[0056] The distance from laser head to part typically ranges from 1
cm to up to 10 cm, or about 3 cm to about 8 cm, while the distance
from powder feed tube to part typically ranges from 1 cm to up to
10 cm, or about 3 cm to about 8 cm.
[0057] In embodiments, controlled and defined parameters for
additive manufacturing methods disclosed herein for continuous
fabrication of components and systems will impart the following
specific properties and characteristics to the built parts:
[0058] geometric dimensions, material adhesion between each layer,
porosity, composition, including gradients, and mechanical and
chemical properties.
[0059] A number of alternatives, modifications, variations, or
improvements therein may be subsequently made by those skilled in
the art, which are also intended to be encompassed by the following
claims.
* * * * *